As the information technology progresses in recent years, a demand for data communication traffic by data communication or the like is increasing. Under this circumstance, broadband communication in a network and reduction in operation cost have been required. A network constituted of radio links such as an FWA (Fixed broadband Wireless Access) employing a wireless system utilizing a frequency of a millimeter wave band or the like capable of broadband transmission is utilized in a mobile phone network or the like.
An FWA is a system configured to connect a plurality of locally placed base stations to each other by wireless communication so as to connect to a core network in a mobile communication system such as a mobile phone. This system has the advantages that the work period can be shortened, as compared with a wired network, and that the cost required for cable placing can be reduced. In recent years, this system is employed by mobile telecommunications carriers, as a connection line for connecting between wireless base stations in a mobile network via a radio link.
A network for configuring an FWA is constituted of radio links. Therefore, communication quality of the network varies according to an SNR (Signal to Noise Ratio) of a receiving signal. In view of the above, in order to implement further broadband communications using a radio link, an adaptive modulation technique has been paid attention to. The adaptive modulation technique is a technique, in which a modulation method having a highest transmission efficiency is adaptively obtained from a radio condition of a radio link for using the modulation method. The adaptive modulation technique makes it possible to perform optimum wireless communication depending on the radio environment, and enhancement of frequency efficiency can be expected.
PTL 1 discloses a path control method, in which a modulation method capable of stably using a radio link is estimated from a history of modulation methods in the past or the like, in view of a point that the band of a radio link changes according to adaptive modulation, and communication quality requested by traffic is secured by using the link band of the estimated modulation method.
However, selecting a radio link of modulation method capable of being used stably under the consideration of stability may lower the traffic accommodation efficiency. Further, according to the path control method as described above, the number of times of hopping the path increases, and the path is likely to be redundant, resulting in an increase in delay even in a path having a high degree of stability.